Comment 6 for bug 1177713

The lightdm solution I propose makes the temporary guest account's real name translated to begin with, i.e. it's the translation of "Guest" that will be saved in the /etc/passwd entry. This should do it in most cases.

However..

If you customize the guest session feature in such a way that a guest session is started with some other language but the system wide language in /etc/default/locale, there will be a mix of languages in the logout dialog. This disadvantage could be avoided if this bug was fixed in Unity instead.

OTOH I suppose it's good to not spread guest session related hacks all over.